Stabilized ferrous compound composition

ABSTRACT

A composition comprising a ferrous compound and as a stabilizer, at least one compound selected from the group consisting of (A) erythorbic acid compounds, (B) hydroxycarboxylic acid compounds and (c) oxocarboxylic acid compounds.

This invention relates to a composition comprising a ferrous compound asa main component, and more specifically, to a novel composition havingimproved stability comprising a ferrous compound and at least onecompound selected from (A) an erythorbic acid compound, (B) ahydroxycarboxylic acid compound and (C) an oxocarboxylic acid compound.

Ferrous compounds such as ferrous sulfate and ferrous chloride are usedas raw materials for the production of deodorants, black iron oxide,mordants, sewage treating agents, medicines, leather-making chemicals,red iron oxide, etc. These iron compounds, whether as an aqueoussolution or a crystal powder, are susceptible to oxidation by oxygenpresent in air or water. This leads to the trouble that within shortperiods of time, they are changed to ferric compounds and colored, orthey are precipitated and consumed.

Attempts have been made to overcome this trouble. For example, JapaneseLaid-Open Patent Publication No. 156539/1983 discloses the addition ofL-ascorbic acid to an aqueous solution of a ferrous compound, andJapanese Laid-Open Patent No. 142856/1985 proposes the powderization ofthe aqeuous solution obtained by the method of the first-mentionedJapanese patent document by drying. These methods, however, have thedefect that the stabilizers used are limited to expensive L-ascorbicacid, and the use of this stabilizer alone produces no sufficientstabilizing effect.

It is an object of this invention to remove these defects of the priorart.

Extensive investigations of the present inventors have now led to thediscovery that ferrous compounds can be stabilized for a long period oftime even in air by incorporating at least one compound selected from(A) erythorbic acid compounds, (B) hydroxycarboxylic acid compounds and(C) oxocarboxylic acid compounds in the ferrous compounds.

Thus, according to this invention, there is provided an iron compoundcomposition comprising a ferrous compound and as a stabilizer at leastone compound selected from the group consisting of (A) erythorbic acidcompounds, (B) hydroxycarboxylic acid compounds and (C) oxocarboxylicacid compounds.

Specific examples of the ferrous compounds are ferrous sulfate (FeSO₄),ferrous chloride (FeCl₂) and ferrous nitrate [Fe(NO₃)₂ ]. Ferroussulfate is most preferred in view of its cost and availability. When theferrous compound is used in the form of an aqueous solution, theconcentration of the ferrous compound may be selected as desired withina range of concentrations which enable the ferrous compound to dissolvein water.

The erythorbic acid compounds (A) are known as an antioxidant for foods,etc. It has however been found for the first time by the presentinventors that the erythorbic acid compounds (A) produce a marked effectas a stabilizer for ferrous compounds which are very susceptible tooxidation The compounds (A) may include both erythorbic acid itself, andits salts such as sodium and potassium salts.

The hydroxycarboxylic acid compounds (B) are hydroxycarboxylic acidscontaining at least one hydroxyl group and at least one carboxyl groupin the molecule, or salts of these acids. Specific examples includealiphatic or aromatic compounds preferably having 2 to 8 carbon atoms,such as lactic acid, hydroxyacetic acid, hydroxybutyric acid, malicacid, tartaric acid, glyceric acid, citric acid, alpha-methylmalic acid,beta-hydroxyglutaric acid, desoxalic acid, monoethyl tartrate, monoethylcitrate, gluconic acid, galactaric acid, glucronic acid, ketogluconicacid, salicylic acid, p-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid,gallic acid and hydroxyphthalic acid, and salts of these acids such assodium, potassium and ammonium salts. The aliphatic compounds and theirsalts are preferred.

The oxocarboxylic acid compounds (C) are oxocarboxylic acids containingat least one aldehyde or keto group and at least one carboxyl group inthe molecule. Specific examples include compounds preferably having 2 to8 carbon atoms, such as glyoxylic acid, malonaldehydic acid,succinaldehydic acid, pyruvic acid, 2-ketobutyric acid, 4-acetylbutyricacid, 2-ketoglutaric acid, 4-keto-n-valeric acid, acetoacetic acid,oxomalonic acid, oxaloacetic acid and acetonedicarboxylic acid, andtheir salts such as sodium, potassium and ammonium salts.

These compounds (A), (B) and (C) may be used in combinations.Particularly, the use of the compound (A) in combination with thecompound (B) and/or the compound (C) gives a synergistic improvingeffect as compared with the use of them singly. The mixing proportionsof these in such a case may be selected as desired. Usually, 1 to 99mole% of the compound (A) is used in combination with 99 to 1 mole% ofthe compound (B) and/or the compound (C). Preferably, 10 to 90 mole% ofthe compound (A) is used in combination with 90 to 10 mole% of thecompounds (B) and/or the compound (C). More preferably, 20 to 80 mole%of the compound (A) is used together with 80 to 20 mole% of the compound(B) and/or the compound (C).

The amount of the stabilizer may be selected depending upon theproperties required of the final composition. Usually, it is at least0.5% by weight, preferably 0.5 to 20% by weight, and more preferably 1to 10% by weight, based on the iron content of the ferrous compound. Ifthe amount is excessively small, the stabilizing effect is insufficient.Excessively large amounts are economically disadvantageous.

The iron compound-containing composition may be in the form of anaqueous solution or a powder so long as it comprises the ferrouscompound and the particular stabilizer described. The composition as anaqueous solution can be obtained by mixing an aqueous solutioncontaining the ferrous compound with a water-soluble stabilizer selectedfrom the above-specified stabilizer compounds. The powdery compositionmay be obtained by drying the aforesaid aqueous solution in a customarymanner. For example, the aqueous solution is spray-dried, or underreduced pressure, at a temperature of not more than 150° C., preferablynot more than 100° C. Alternatively, it may be obtained by mechanicallymixing the ferrous compound in the form of a crystal powder with apowdery stabilizer of the specified group or a solution or dispersion ofthe stabilizer in water or a solvent. Desirably, the mixing temperaturein this method is adjusted to not more than 150° C., preferably not morethan 100° C. If the mixing temperature is excessively high, thestabilizer may undergo decomposition, or water of crystallization may beliberated from the ferrous compound. Such troubles will reduce theproductivity.

The present invention can increase the stability of ferrous compounds ascompared with known techniques using ascorbic acid. Powders or aqueoussolutions of ferrous compounds so stabilized, either as such orimpregnated in various carriers, can be widely used as raw materials fordeodorants, water treating agents, mordants, medicines, pigments, moldproofing agents, bactericides, oxygen absorbing agents, etc.

The following examples illustrate the present invention morespecifically.

EXAMPLE 1

In each run, a predetermined amount of erythorbic acid was dissolved inan aqueous solution of ferrous sulfate having an iron concentration of50 g/liter. One hundred milliliters of the aqueous solution was put in a100 ml. beaker, and a glass plate was placed on the beaker. The beakerwas left to stand, and the color of the aqueous solution and the time offormation of a precipitate were observed. The results are shown in Table1.

It is seen from the results given in Table 1 that when no stabilizer wasused (Run No. 1-1), a precipitate formed within a short period of time,and the stability of the iron compound was inferior, whereas whenerythorbic acid was added, the iron compound remained stable over a longperiod of time.

                                      TABLE 1                                     __________________________________________________________________________    Erythorbic acid                                                                        Propor-                                                                       tion                                                                     Concen-                                                                            based                                                                Run tration                                                                            on Fe                                                                              Changes with time (*)                                           No. (g/l)                                                                              (%)  1st day                                                                             2nd day                                                                            3rd day                                                                             4th day                                                                           5th day                                                                           6th day                                                                            7th day                                                                           8th day                                                                            9th                                                                               10th                 __________________________________________________________________________                                                             day                  Control                                                                       1-1 0    0    Yellow-                                                                             Precipi-                                                                ish green                                                                           tated                                                                   Turbid                                                          Invention                                                                     1-2 1    2    Pale  →                                                                           →                                                                            →                                                                          Green                                                                             →                                                                           →                                                                          →                                                                           →                                                                          →                           blue                                                                          Trans-                                                                              →                                                                           →                                                                            →                                                                          →                                                                          →                                                                           →                                                                          →                                                                           →                                                                          →                           parent                                                          1-3 1.5  3    Pale  →                                                                           →                                                                            →                                                                          →                                                                          →                                                                           →                                                                          →                                                                           →                                                                          →                           blue                                                                          Trans-                                                                              →                                                                           →                                                                            →                                                                          →                                                                          →                                                                           →                                                                          →                                                                           →                                                                          →                           parent                                                          1-4 3    6    Pale  →                                                                           →                                                                            →                                                                          →                                                                          →                                                                           →                                                                          →                                                                           →                                                                          →                           blue                                                                          Trans-                                                                              →                                                                           →                                                                            →                                                                          →                                                                          →                                                                           →                                                                          →                                                                           →                                                                          →                           parent                                                          1-5 5    10   Pale  →                                                                           →                                                                            →                                                                          →                                                                          →                                                                           →                                                                          →                                                                           →                                                                          →                           blue                                                                          Trans-                                                                              →                                                                           →                                                                            →                                                                          →                                                                          →                                                                           →                                                                          →                                                                           →                                                                          →                           parent                                                          __________________________________________________________________________    Erythorbic acid                                                                        Propor-                                                                       tion                                                                 Concen-  based                                                                              Changes with time (*)                                           Run tration                                                                            on Fe                                                                              11th    13th                                                                             14th                                                 No. (g/l)                                                                              (%)  day                                                                              12th day                                                                           day                                                                              day                                                                              15th day                                                                           16th day                                                                           17th day                                                                           18th day                                                                           19th day                                                                           20th                                                                               21st                __________________________________________________________________________                                                              day                 Control                                                                       1-1 0    0                                                                    Invention                                                                     1-2 1    2    →                                                                         →                                                                           →                                                                         →                                                                         →                                                                           →                                                                           Yellow-                                                                            →                                                                           →                                                                           →                                                                           Precipi-                                                  ish green           tated                             →                                                                         →                                                                           →                                                                         →                                                                         →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           Turbid                   1-3 1.5  3    →                                                                         Green                                                                              →                                                                         →                                                                         →                                                                           →                                                                           →                                                                           Yellow-                                                                            →                                                                           →                                                                           Blackish                                                       ish green      yellow                            →                                                                         →                                                                           →                                                                         →                                                                         →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →            1-4 3    6    →                                                                         Green                                                                              →                                                                         →                                                                         →                                                                           →                                                                           →                                                                           Yellow-                                                                            →                                                                           →                                                                           Blackish                                                       ish green      yellow                            →                                                                         →                                                                           →                                                                         →                                                                         →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →            1-5 5    10   →                                                                         Green                                                                              →                                                                         →                                                                         →                                                                           →                                                                           →                                                                           Yellow-                                                                            →                                                                           →                                                                           Blackish                                                       ish green      yellow                            →                                                                         →                                                                           →                                                                         →                                                                         →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →            __________________________________________________________________________     (*) The upper rows indicate the changes in the colors of the aqueous          solutions, and the lower rows, the changes in the transparency of the         aqueous solution. The indication "precipitated" means that a precipitate      formed and further observation was stopped.                              

EXAMPLE 2

Run No. 1-4 of Example 1 was repeated except that sodium erythorbate wasused instead of erythorbic acid. The results obtained were substantiallythe same as those obtained in Run No. 1-4 of Example 1.

EXAMPLE 3

In each run, a predetermined amount of each of the hydroxycarboxylicacids indicated in Table 2 was used instead of erythorbic acid. Theresults are shown in Table 2.

The results shown in Table 2 demonstrate that the iron compound wasstable over a long period of time also when the hydroxycarboxylic acidswere incorporated.

                                      TABLE 2                                     __________________________________________________________________________    Sample                                                                                Concen-                                                               Run Stabi-                                                                            tration                                                                            Changes with time (*)                                            No. lizer                                                                             (g/l)                                                                              1st day                                                                             2nd day                                                                            3rd day                                                                            4th day                                                                           5th day                                                                            6th day                                                                            7th day                                                                           8th day                                                                           9th day                    __________________________________________________________________________    Control                                                                       3-1 None                                                                              0    Yellow-                                                                             Precipi-                                                                ish green                                                                           tated                                                                   Turbid                                                           Invention                                                                     3-2 Tar-                                                                              1    Yellow-                                                                             →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           Yellow                                                                            →                                                                          →                       taric    ish green                                                            acid     Trans-                                                                              →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           →                                                                          →                                                                          →                                parent                                                           3-3     2    Yellow                                                                              →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           →                                                                          →                                                                          →                                ish green                                                                     Trans-                                                                              →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           →                                                                          →                                                                          →                                parent                                                           3-4     3    Yellow                                                                              →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           →                                                                          →                                                                          →                                ish green                                                                     Trans-                                                                              →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           →                                                                          →                                                                          →                                parent                                                           3-5 Gluco-                                                                            1    Yellow                                                                              →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           Yellow                                                                            →                                                                          →                       nic      ish green                                                            acid     Trans-                                                                              →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           →                                                                          →                                                                          →                                parent                                                           3-6     2    Yellow-                                                                             →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           →                                                                          →                                                                          →                                ish green                                                                     Trans-                                                                              →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           →                                                                          →                                                                          →                                parent                                                           3-7     3    Yellow-                                                                             →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           →                                                                          →                                                                          →                                ish green                                                                     Trans-                                                                              →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           →                                                                          →                                                                          →                                parent                                                           3-8 Citric                                                                            1    Yellow-                                                                             →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           →                                                                          →                                                                          →                       acid     ish green                                                                     Trans-                                                                              →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           →                                                                          →                                                                          →                                parent                                                           3-9     2    Yellow-                                                                             →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           →                                                                          →                                                                          →                                ish green                                                                     Trans-                                                                              →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           →                                                                          →                                                                          →                                parent                                                            3-10                                                                             Maleic                                                                            1    Green →                                                                           →                                                                           →                                                                          Yellow-                                                                            →                                                                           Yellow                                                                            →                                                                          Blackish                       acid           →                                                                           →                                                                           →                                                                          ish green                                                                          →                                                                           →                                                                          →                                                                          yellow                                  Trans-                                                                              →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           →                                                                          →                                                                          →                                parent                                                            3-11   2    Green →                                                                           →                                                                           →                                                                          Yellow-                                                                            →                                                                           Yellow                                                                            →                                                                          →                                      →                                                                           →                                                                           →                                                                          ish green                                                                          →                                                                           →                                                                          →                                                                          →                                Trans-                                                                              →                                                                           →                                                                           →                                                                          →                                                                           →                                                                           →                                                                          →                                                                          →                                parent                                                           __________________________________________________________________________    Sample                                                                               Concen                                                                 Run                                                                              Stabi-                                                                            tration                                                                            Changes with time (*)                                             No.                                                                              lizer                                                                             (g/l)                                                                              10th day                                                                           11th day                                                                           12th day                                                                           13th day                                                                           14th day                                                                           15th day                                                                           16th day                                                                           20th day                                                                           21st                      __________________________________________________________________________                                                        day                       Control                                                                       3-1                                                                              None                                                                              0                                                                      Invention                                                                     3-2                                                                              Tar-                                                                              1    →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           Orange                                                                             →                                                                           →                                                                           →                     taric    →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                     acid                                                                       3-3    2    →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           Yellow                                →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                  3-4    3    →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           Yellow                                →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                  3-5                                                                              Gluco-                                                                            1    →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           Orange                                                                             →                                                                           →                                                                           →                     nic      →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           Turbid                                                                             →                     acid                                                                       3-6    2    →                                                                           →                                                                           →                                                                           →                                                                           Yellow                                                                             →                                                                           →                                                                           →                                                                           →                              →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                  3-7    3    →                                                                           →                                                                           →                                                                           →                                                                           Yellow                                                                             →                                                                           →                                                                           →                                                                           →                              →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                  3-8                                                                              Citric                                                                            1    →                                                                           →                                                                           →                                                                           →                                                                           Precipi-                                         acid                         tated                                                     →                                                                           →                                                                           →                                                                           Turbid                                             3-9    2    →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           Blackish                                                                      yellow                                →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                   3-10                                                                            Maleic                                                                            1    →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           Precipi-                               acid                                   tated                                           →                                                                           →                                                                           →                                                                           →                                                                           Turbid                                                                             →                                  3-11  2    Blackish                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                              yellow                                                                        →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                  __________________________________________________________________________     (*) Same as the footnote to TABLE 1.                                     

EXAMPLE 5

Example 1 was repeated except that each of the oxocarboxylic acids shownin Table 3 was used instead of erythorbic acid. The results are shown inTable 3.

The results shown in Table 3 demonstrate that when the oxocarboxylicacids were incorporated, the iron compound also remained stable over along period of time.

                                      TABLE 3                                     __________________________________________________________________________    Sample                                                                                 Concen-                                                              Run Stabi-                                                                             tration                                                                            Changes with time (*)                                           No. lizer                                                                              (g/l)                                                                              1st day                                                                             2nd day                                                                            3rd day                                                                            4th day                                                                            5th day                                                                            6th day                                                                            7th day                                                                           8th day                                                                           9th                                                                                10th                __________________________________________________________________________                                                              day                 Control                                                                       5-1 None 0    Yellow-                                                                             Precipi-                                                                ish green                                                                           tated                                                                   Turbid                                                          Invention                                                                     5-2 2-keto-                                                                            1    Pale  →                                                                           →                                                                           →                                                                           Blackish                                                                           →                                                                           →                                                                          →                                                                          →                                                                           →                glu-      brown                brown                                          taric     Trans-                                                                              →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                          →                                                                          →                                                                           →                acid      parent                                                          5-3      2    Pale  →                                                                           →                                                                           →                                                                           Light                                                                              →                                                                           →                                                                          →                                                                          →                                                                           →                          brown                brown                                                    Trans-                                                                              →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                          →                                                                          →                                                                           →                          parent                                                          5-4      3    Pale  →                                                                           →                                                                           →                                                                           Light                                                                              →                                                                           →                                                                          →                                                                          →                                                                           →                          brown                brown                                                    Trans-                                                                              →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                          →                                                                          →                                                                           →                          parent                                                          5-5 Pyruvic                                                                            1    Pale  →                                                                           →                                                                           →                                                                           Blackish                                                                           →                                                                           →                                                                          →                                                                          →                                                                           →                acid      yellow               yellow                                                   Trans-                                                                              →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                          →                                                                          →                                                                           Turbid                            parent                                                          5-6      2    Pale  →                                                                           →                                                                           →                                                                           Blackish                                                                           →                                                                           →                                                                          →                                                                          Brown                                                                              →                          brown                yellow                                                   Trans-                                                                              →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                          →                                                                          →                                                                           →                          parent                                                          5-7      3    Pale  →                                                                           →                                                                           →                                                                           Blackish                                                                           →                                                                           →                                                                          →                                                                          Brown                                                                              →                          brown                yellow                                                   Trans-                                                                              →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                          →                                                                          →                                                                           →                          parent                                                          5-8 Gly- 1    Yellow-                                                                             →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                          →                                                                          Yellow                                                                             →                oxylic    ish green                                                           acid      Trans-                                                                              →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                          →                                                                          →                                                                           →                          parent                                                          5-9      2    Yellow-                                                                             →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                          →                                                                          Yellow                                                                             →                          ish green                                                                     Trans-                                                                              →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                          →                                                                          →                                                                           →                          parent                                                          5-10     3    Yellow-                                                                             →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                          →                                                                          Yellow                                                                             →                          ish green                                                                     Trans-                                                                              →                                                                           →                                                                           →                                                                           →                                                                           →                                                                           →                                                                          →                                                                          →                                                                           →                          parent                                                          __________________________________________________________________________    Sample                                                                                 Concen-                                                                            Changes with time (*)                                           Run Stabi-                                                                             tration                                                                            11th    13th              17th                                  No. lizer                                                                              (g/l)                                                                              day                                                                              12th day                                                                           day                                                                              14th day                                                                           15th day                                                                           16th day                                                                           day                                                                              18th day                                                                           19th day                                                                           20th                                                                               21st                __________________________________________________________________________                                                              day                 Control                                                                       5-1 None 0                                                                    Invention                                                                     5-2 2-keto-                                                                            1    →                                                                         Precipi-                                                         glu-      →                                                                         tated                                                            taric                                                                         acid                                                                      5-3      2    →                                                                         →                                                                           →                                                                         Reddish                                                                            →                                                                           →                                                                           →                                                                         →                                                                           Precipi-                                               brown                  tated                                       →                                                                         →                                                                           →                                                                         →                                                                           →                                                                           Turbid                                                                             →                                                                         →                           5-4      3    →                                                                         →                                                                           →                                                                         Reddish                                                                            →                                                                           →                                                                           →                                                                         →                                                                           Precipi-                                               brown                  tated                                       →                                                                         →                                                                           →                                                                         →                                                                           →                                                                           →                                                                           →                              5-5 Pyruvic                                                                            1    →                                                                         Precipi-                                                         acid      →                                                                         tated                                                        5-6      2    →                                                                         →                                                                           →                                                                         →                                                                           →                                                                           →                                                                           →                                                                         →                                                                           Light                                                                              →                                                                           →                                                            brown                                       →                                                                         →                                                                           →                                                                         →                                                                           →                                                                           →                                                                           →                                                                         →                                                                           →                                                                           →                                                                           →            5-7      3    →                                                                         →                                                                           →                                                                         →                                                                           →                                                                           →                                                                           →                                                                         →                                                                           Light                                                                              →                                                                           →                                                            brown                                       →                                                                         →                                                                           →                                                                         →                                                                           →                                                                           →                                                                           →                                                                         →                                                                           →                                                                           →                                                                           →            5-8 Gly- 1    →                                                                         →                                                                           →                                                                         →                                                                           →                                                                           →                                                                           →                                                                         →                                                                           Precipi-                          oxylic                                      tated                             acid      →                                                                         →                                                                           →                                                                         →                                                                           →                                                                           →                                                                           →                                                                         Turbid                             5-9      2    →                                                                         →                                                                           →                                                                         →                                                                           →                                                                           →                                                                           →                                                                         →                                                                           →                                                                           →                                                                           →                          →                                                                         →                                                                           →                                                                         →                                                                           →                                                                           →                                                                           →                                                                         →                                                                           →                                                                           →                                                                           →             5-10    3    →                                                                         →                                                                           →                                                                         →                                                                           →                                                                           →                                                                           →                                                                         →                                                                           →                                                                           →                                                                           →                          →                                                                         →                                                                           →                                                                         →                                                                           →                                                                           →                                                                           →                                                                         →                                                                           →                                                                           →                                                                           →            __________________________________________________________________________     (*) Same as the footnote to TABLE 1.                                     

EXAMPLE 6

In each run, each of the stabilizers indicated in Table 4 was dissolvedin a concentration of 1 g/liter in an aqueous solution of ferroussulfate having an iron concentration of 50 g/liter. One hundredmilliliters of the aqueous solution was put in a 100 ml beaker, and aglass plate was put over it. The beaker was left to stand for 20 days,and the color of the aqueous solution and the formation of a precipitatewere observed.

                  TABLE 4                                                         ______________________________________                                        Amount of the stabilizer added (mole %)                                       Stabilizer                                                                            Control          Invention                                            ______________________________________                                        Erythorbic                                                                            100      0       0     60    40  60   40                              acid                                                                          Gluconic                                                                              0        100     0     40    60   0    0                              acid                                                                          Glyoxylic                                                                             0        0       100    0     0  40   60                              acid                                                                          State after                                                                           Precipitated     Yellowish green and                                  20-day                   transparent                                          standing                                                                      ______________________________________                                    

It is seen from the above results that when erythorbic acid, gluconicacid and glyoxylic acid were used jointly, the stability of the ironcompound was much better than when they were used singly.

EXAMPLE 7

Ferrous sulfate (FeSO₄.7H₂ O; 275 g) was dissolved in distilled waterpurged with nitrogen to prepare an aqueous solution (1000 ml). Fivegrams (9% based on Fe) of each of the stabilizers indicated in Table 5was dissolved in the aqueous soution to prepare an aqueous solutioncontaining ferrous sulfate and the stabilizer. The aqueous solution wasspray-dried by a spray dryer (Model GA-31, made by Yamato Science Co.,Ltd.) under the following conditions to form a powdery composition.

Amount of the aqueous solution passed: 35 ml/min.

Flow rate of drying air: 0.6 m³ /min.

Inlet temperature: 120° C.

Ten grams of the powdery composition was taken into a glass Petri dish,and the dish was left to stand in a hot air oven at 80° C. Changes inthe outer appearance of the composition with time were observed. Then,the composition was taken out and dissolved in water to prepare anaqueous solution. Changes in the appearance of the aqueous solution withtime were also observed. The results are shown in Table 5.

For comparison, the same experiment as above was conducted without usingany stabilizer or by using L-ascorbic acid as the stabilizer. Theresults are also shown in Table 5.

The results given in Table 5 demonstrate the higher stability of theiron compound stabilized by the stabilizer in accordance with thisinvention than that stabilized with L-ascorbic acid.

                                      TABLE 5                                     __________________________________________________________________________                 Changes in appearance                                                                       Stability of the 40%                                            with time     aqueous solution (*)                                            Immediately   Immediately                                                     after pre-                                                                           After  after pre-                                                                           After                                       Run No.                                                                            Stabilizer                                                                            paration                                                                             1.5 hours                                                                            paration                                                                             1.5 hours                                   __________________________________________________________________________    Invention                                                                     7-1  Erythorbic acid                                                                       Pale brown                                                                           Brown  O      O                                           7-2  Tartaric acid                                                                         White  Pale yellow-                                                                         O      O                                                               ish white                                                 7-3  Citric acid                                                                           Pale brown                                                                           Pale brown                                                                           O      O                                           7-4  Gluconic acid                                                                         Pale green                                                                           Pale yellow-                                                                         O      O                                                               ish green                                                 7-5  Glyoxylic acid                                                                        Pale bluish                                                                          Pale bluish                                                                          O      O                                                        white  white                                                     Control                                                                       7-6  None    Pale bluish                                                                          Brown  X      X                                                        white                                                            7-7  L-ascorbic acid                                                                       Pale brown                                                                           Brown  O      X                                           __________________________________________________________________________     (*): Evaluated by O which shows that the solution was a uniform               transparent solution, and X which shows that a precipitate formed.       

EXAMPLE 8

In each run, each of the stabilizers indicated in Table 6 was added inan amount of 9% based on Fe to 275 g of crystals of ferrous sulfate, andthe mixture was worked up by a mortar to form a white powderycomposition.

Ten grams of the powdery composition was taken into a glass Petri dish.The Petri dish was left to stand at 20° C. for 10 days in a desiccatorkept at a humidity of 79%, and changes in the outside appearance of thepowdery composition were observed. After this test, the powderycomposition was taken out and dissolved in water to form a 40% aqueoussolution. Changes in the appearance of the aqueous solution were alsoobserved. The results are shown in Table 6.

For comparison, the above experiment was repeated without using thestabilizer. The results are also shown in Table 6.

It is seen from Table 6 that the composition of this invention hasbetter stability.

                                      TABLE 6                                     __________________________________________________________________________                 Changes in appearance                                                                         Stability of the 40%                                          with time       aqueous solution (*)                                          Immediately     Immediately                                                   after prep-                                                                           After   after prep-                                                                          After                                     Run No.                                                                            Stabilizer                                                                            aration 1.5 hours                                                                             aration                                                                              10 days                                   __________________________________________________________________________    Invention                                                                     8-1  Erythorbic acid                                                                       Bluish white                                                                          Bluish white                                                                          O      O                                         8-2  Tartaric acid                                                                         Bluish white                                                                          Bluish white                                                                          O      O                                         8-3  40% aqueous                                                                           Greenish white                                                                        Greenish white                                                                        O      O                                              gluconic acid                                                                 solution                                                                 8-4  40% aqueous                                                                           Greenish white                                                                        Greenish white                                                                        O      O                                              glyoxylic acid                                                                solution                                                                 Control                                                                       8-5  None    Bluish white                                                                          Bluish white                                                                          X      X                                         __________________________________________________________________________     (*): Same as the footnote to TABLE 5.                                    

EXAMPLE 9

Ten grams of each of the powdery compositions obtained in Runs Nos. 8-2to 8-4 of Example 8 was taken into a glass Petri dish. The Petri dishwas left to stand in a hot air oven at 80° C., and changes in theappearance of the powdery composition with time were observed. After thetest, the powdery composition was taken out and dissolved in water toprepare a 40% aqueous solution. Then, changes in the appearance of theaqueous solution with time were observed. The results are shown in Table7.

For comparison, the same test was repeated except that no stabilizer wasused. The results are also shown in Table 7.

The results shown in Table 7 demonstrate the superiority of thecomposition of this invention.

                                      TABLE 7                                     __________________________________________________________________________                Changes in appearance                                                                         Stability of the 40%                                          with time       aqueous solution (*)                                          Immediately     Immediately                                                   after pre-                                                                            After   after pre-                                                                           After                                      Run No.                                                                            Stabilizer                                                                           paration                                                                              1.5 hours                                                                             paration                                                                             1.5 hours                                  __________________________________________________________________________    Invention                                                                     9-1  Tartaric acid                                                                        Bluish white                                                                          Greenish white                                                                        O      O                                          9-2  40% aqueous                                                                          Greenish white                                                                        Greenish white                                                                        O      O                                               gluconic acid                                                                 solution                                                                 9-3  40% aqueous                                                                          Greenish white                                                                        Greenish white                                                                        O      O                                               glyoxylic acid                                                                solution                                                                 Control                                                                       9-4  None   Bluish white                                                                          Light brown                                                                           X      X                                          __________________________________________________________________________     (*): Same as the footnote to TABLE 5.                                    

What we claim is:
 1. A composition consisting essentially of a ferrouscompound selected from the group consisting of ferrous sulfate, ferrouschloride and ferrous nitrate and as a stabilizer, at least one compoundselected from the group consisting of (A) erythorbic acid compounds, (B)hydroxycarboxylic acid compounds having 2 to 8 carbon atoms and (C)oxocarboxylic acid compounds having 2 to 8 carbon atoms and, optionally,water.
 2. The composition of claim 1 which is in the form of an aqueoussolution.
 3. The composition of claim 1 which is in the form of apowder.
 4. The composition of claim 3 which is obtained by drying thecomposition of claim
 2. 5. The composition of claim 3 obtained by mixinga powder of the ferrous compound with the stabilizer compound.
 6. Thecomposition of claim 1 wherein the amount of the stabilizer compound is0.5 to 20% by weight based on the iron content of the ferrous compound.7. The composition of claim 1 wherein the hydroxycarboxyclic acidcompounds are aliphatic compounds.
 8. The composition of claim 1 whereinthe oxocarboxylic acid compounds are aliphatic compounds.
 9. Thecomposition of claim 1 wherein the stabilizer compound is a mixture ofthe compound (A) with the compound (B) and/or the compound (C).
 10. Thecomposition of claim 1 wherein the stabilizer compound is a mixture ofthe compound (A) with the compound (B) or the compound (C) in a moleratio of 20:80 to 80:20.
 11. The composition of claim 1 wherein thestabilizer is the hydroxycarboxylic acid compound (B) and is selectedfrom the group consisting of lactic acid, hydroxyacetic acid,hydroxybutyric acid, malic acid, tartaric acid, glyceric acid, citricacid, alpha-methylmalic acid, beta-hydroxglutaric acid, desoxalic acid,monoethyl tartrate, monoethyl citrate, gluconic acid, galactaric acid,glucronic acid, ketogluconic acid, salicylic acid, p-hydroxybenzoicacid, 2,4-dihydroxybenzoic acid, gallic acid, hydroxyphthalic acid andthe salts thereof.
 12. The composition of claim 1 wherein the stabilizeris the oxocarboxylic acid compound (C) and contains at least onealdehyde or keto group and at least one carboxyl group in the molecule.13. The composition of claim 1 wherein the stabilizer is thehydroxycarboxylic acid compound (B) and contains at least one hydroxylgroup and at least one carboxyl group in the molecule.
 14. Thecomposition of claim 1 wherein the stabilizer is the oxocarboxylic acidcompound (C) and is selected from the group consisting of glyoxylicacid, malonaldehydic acid, succinaldehydic acid, pyruvic acid,2-ketobutyric acid, 4-acetylbutyric acid, 2-ketoglutaric acid,4-keto-n-valeric acid, acetoacetic acid, oxomalonic acid, oxaloaceticacid, acetonedicarboxylic acid and the salts thereof.
 15. Thecomposition of claim 1 wherein the stabilizer is the erythorbic acidcompound (A) and is selected from the group consisting of erythorbicacid and the sodium and potassium salts thereof.